Buzzing noise with Klipsch RF62 horns

Hi, I got a problem with my Sony DA2400ES and my Klispch speakers. When I play movies with lound bass (think to the opening of Jurassic Park or Avatar) I hear a buzzing noise from the horns of the Klipsch RF62. I tried to play with the crossover frequency with the 2400ES and when I set the front at 80hz most of the buzzing goes away. At 150hz, there's no buzzing. Note that the buzzing noise only come from the horns.

Here's my setup :
Sony DA2400ES decoder
Cheapo 18awg cable (temporary)
Front Klispch RF-62 (connected to FRONT A)
Center Klipsch RC-64
Rear RS-62
And a PSW10D sub connected via LFE RCA (the white one on the AVR)

Thank you very, very much in advance for you help!